The invention relates to an infinitely variable traction roller transmission in which motion transmitting traction rollers are disposed between, and in engagement with, opposite toric discs mounted on input and output shafts.
To enable such toroidal traction roller transmissions to transmit large torques, large engagement forces between the toric discs and the traction rollers are necessary, which forces are generally obtained by forcing the toric discs toward each other and into firm engagement with the traction rollers therebetween. The engagement forces depend on, and are generated by, the torque transmitted through the transmissions. This, however, results in a large axial thrust load of the traction rollers and the support structure for the rollers.
In order to avoid that the transmission housing has to carry this load, opposite roller support structures have been interconnected by tension sheets which take up the opposing forces applied to the traction rollers during operation of the transmission. Furthermore, this arrangement--as claimed and disclosed in this applicant's U.S. Pat. No. 3,810,398--prevents excessive vibration from being transmitted to the transmission housing as the tension sheets balance the forces and, furthermore, provide for a limited freedom of movement of the roller support structure relative to the transmission housing.
In a present design and as shown in U.S. Pat. No. 4,086,820, the tension sheets are anchored to the transmission housing which, although this permits flexure of the tension sheets, provides for no freedom of movement of a tension sheet as a whole. The tension sheets therefore determine the position of the roller support structure, that is the position of the traction rollers, which in turn determines the position of the toric disc shafts. Although there is normally sufficient bearing clearance it has been found that the traction roller support structures do not have sufficient axial freedom, at least not under light loads. As a result light load or no load losses are relatively high and are dependent on the tolerances.
For best light load efficiency, both disc shafts ought to be supported on anti-friction bearings which do not allow axial movement of the shafts. Therefore, the traction roller support structure should be so mounted that slight position adjustment is possible for the traction roller support structures to find the true geometric center of the traction rollers with regard to the traction discs and movement necessary to find such center should not be restricted by forces applied to the traction roller support structure through the tension sheets from the housing or the opposite traction roller support structure connected to the same tension sheets.